The periodic analysis of Public Health England (PHE) published on June 3 notes that the Delta variant (the new name of B.1.617.2, the former Indian variant) became prevalent in Great Britain, of about 50% more transmissible of the Alpha variant (formerly English) and increases by 2 and a half times the risk of hospitalization. The non-optimistic picture was completed by a work just published in the scientific journal The Lancet (also on June 3) which detects a Delta’s greater resistance to Covid vaccines, especially after a single dose.
Confirmed cases of the variant in the UK rose to 12,431, up from 6,959 the week before, and account for up to 75% of new coronavirus cases. With respect to the higher transmissibility, the PHE estimate of Secondary Attack Rate Delta’s (SAR) dropped, from 67% higher than Alpha in last week’s report, to + 50% this week. The SAR tells us how likely someone is to infect one of its close contacts, so Delta confirms hers potential greater contagiousness.
Risk of hospitalization
Analysis of 38,805 sequenced cases in England also revealed that the Delta variant would be associated with a 2.61 times greater risk of hospitalization (within 14 days from the date of the sample) compared to the Alpha variant.
73% of unvaccinated cases
The good news that vaccination still appears to have a marked impact on prevalence: the 73% of Delta cases involve unvaccinated people and only 3.7% of people who received both doses, while only 5% of people hospitalized with this variant were fully vaccinated. There is no increase in the numbers of reinfections in the cohort of national SIREN health workers which is constantly monitored.
Less protected after the first dose
The PHE report came along with research published in Lancet by the scientists of the Francis Crick Institute he was born in National Institute for Health Research, which shows a reduced plasma neutralization activity of people vaccinated against the Delta variant compared to the Alpha variant, particularly after the first dose. The study, which involved analyzing blood samples from 250 healthy people who received one or two injections of the Pfizer / BioNTech vaccine, showed that neutralizing antibody levels are, on average, lower than those that can address the Delta variant compared to the original strain of SARS-CoV-2 or the Alpha variant. 79% of the vaccinated with one dose had a neutralizing response of antibodies against the Alpha virus reduced to 50% (compared to the original strain) 32% with the Delta variant and 25% with the Beta variant (formerly South African). The cohort analyzed in the study had an average age of 40, was healthy and recently vaccinated. Immunity may be even lower in older or weaker people. However, laboratory tests on neutralizing antibodies are not the same as the immunity that an individual acquires, which is usually more solid, but they do give a useful indication. Levels of neutralizing antibodies against each variant were higher after two doses. The increased protection is confirmed by real-world data, where repeated analyzes continue to show that the efficacy of the vaccine against Delta is greater after 2 doses.
UK government decisions
With the prevalence of the Delta variant increasing across all regions of the UK, the country must decide how to continue with the reopening program. The government last month has lifted the obligation for students of secondary schools to wear masks in the classrooms. The PHE surveillance report shows that infection rates are highest in all educational settings: primary and secondary. And the growth of cases in the secondary cycle is not due to an increase in tests, which have decreased significantly and are based only on symptomatic cases, which notoriously underestimate infection among children and epidemics in schools. It therefore seems that there have been about 40 outbreaks in primary and secondary schools in the week alone until May 30th. To maximize population coverage, the UK delayed the second dose from 3 weeks to around 12 weeks in early 2021. This proved to be a good strategy for the Alpha variant, but if it were confirmed that single dose vaccine recipients they have a lower ability to neutralize Delta, some choices should be reconsidered. Currently in the UK the percentage of the population vaccinated with one dose at 59.26% and with two doses at 39.03%.
June 5, 2021 (change June 5, 2021 | 10:10)
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